Precursors to herbicidal pyridine compounds

ABSTRACT

This invention relates to certain pyridine derivatives having herbicidal properties, and to herbicidal processes and compositions utilizing them.

This is a continuation of application Ser. No. 431,099, filed Sept. 30,1982 now abandoned, which was abandoned upon the filing hereof, saidSer. No. 431,099 being a cont. of Ser. No. 029,341 filed Apr. 11, 1979.

This invention relates to certain pyridine derivatives having herbicidalproperties, and to herbicidal processes and compositions utilizing them.

According to the present invention there are provided herbicidalpyridine compounds of the formula (I): ##STR1## wherein Z and Y eachrepresents a fluorine, chlorine, bromine, iodine, or hydrogen atom, or atrifluoromethyl, difluoromethyl, or chlorodifluoromethyl radical,provided that at least one of Z and Y is a halogenomethyl radical; R¹represents hydrogen or an alkyl radical of 1 to 4 carbon atoms; and R²is a cyano group; a carboxyl group; a carboxamido group ##STR2## whereinR³ is hydrogen or an alkyl radical and R⁴ is hydrogen, an optionallyhydroxy- or phenyl-substituted alkyl radical of 1 to 4 carbon atoms, aphenyl or chlorophenyl radical, an alkoxy radical of 1 to 4 carbonatoms, or a group --NR⁵ R⁶ wherein R⁵ is hydrogen or alkyl of 1 to 4carbon atoms, and R⁶ is hydrogen, alkyl of 1 to 4 carbon atoms, phenylor chlorophenyl, or the group --NR³ R⁴ constitutes a pyrrolidino,piperidino, or morpholino radical; a group ##STR3## wherein R⁷ is alkylor phenyl; an alkoxycarbonyl group wherein the alkoxy group may bestraight or branched, and which optionally bears one or more hydroxy,alkoxy, or halogen substituents, or bears a substituent of Formula (I)wherein R² represents a ##STR4## radical; a group ##STR5## wherein R⁸ isan alkyl radical of 1 to 4 carbon atoms and n is an integer from 1 to 5inclusive; a cyclohexyloxycarbonyl radical optionally substituted by oneor more halogen atoms or methyl radicals; an alkenyloxycarbonyl radicalin which the alkenyl group contains from 3 to 6 carbon atoms; aphenoxycarbonyl radical optionally bearing one or more halogen or methylsubstituents; or a benzyloxycarbonyl radical, the phenyl group of whichoptionally bears one or more halogen or methyl substituents; and, in thecase of compounds wherein R² is a carboxyl group, salts thereof.

When R³ is an alkyl radical it is preferably an alkyl radical of 1 to 12carbon atoms, for example an alkyl radical of 1 to 4 carbon atoms.

When R⁷ is an alkyl radical it may be for example an alkyl radical of 1to 20 carbon atoms. Examples of alkyl radicals within this range includethose of 1 to 12 carbon atoms, for example methyl, ethyl, propyl, butyl,and dodecyl.

When R² is an alkoxycarbonyl group, the alkoxy group may contain forexample from 1 to 20 carbon atoms; it may for example contain from 1 to12 carbon atoms. Within this range, the alkoxy group may for examplecontain from 1 to 8 carbon atoms. Particular examples of alkoxy groupswithin this range include methoxy, ethoxy, propoxy, butoxy, isobutoxy,secbutoxy, and octyloxy.

Salts of compounds according to the invention wherein R² represents acarboxylic acid may be prepared by conventional methods known for thepreparation of salts of carboxylic acids. Typical salts include metalsalts and ammonium salts. Metal salts include salts formed with alkalimetal cations, for example sodium, potassium and lithium, and alkalineearth metal cations, for example calcium, strontium, and magnesium.Ammonium salts include salts formed with the ammonium cation or with amono-, di-, tri-, or tetra-substituted ammonium cation in which thesubstituents may be, for example, aliphatic radicals of 1 to 6 carbonatoms; these may be, for example, alkyl radicals of 1 to 6 carbon atoms.

One group of compounds according to the invention includes those inwhich the group Z is a CF₃ radical, Y is a hydrogen atom, R¹ is a methylgroup, and R² is as defined above. Within this group, R² may be, forexample, a carboxyl group either as such or in the form of a saltthereof, or may be an alkoxycarbonyl radical, for example analkoxycarbonyl radical in which the alkoxy group contains from 1 to 6carbon atoms.

Another group of compounds according to the invention includes those inwhich the group Z is a CF₃ radical, Y is a chlorine atom, R¹ is a methylgroup, and R² is as defined above. Within this group, R² may be, forexample, a carboxyl group either as such or in the form of a saltthereof, or may be an alkoxycarbonyl radical, for example analkoxycarbonyl radical wherein the alkoxy group contains from 1 to 6carbon atoms.

A further group of compounds according to the invention includes thosein which the group Z is a difluoromethyl or chlorodifluoromethylradical, Y is hydrogen or chlorine, R¹ is a methyl group, and R² is asdefined above. Within this group of compounds, R² may be, for example, acarboxyl group either as such or in the form of a salt thereof, or maybe an alkoxycarbonyl radical, for example an alkoxycarbonyl radicalwherein the alkoxy group contains from 1 to 6 carbon atoms.

The compounds of the invention, apart from those in which the group R¹in Formula (I) is a hydrogen atom, contain an asymmetric carbon atom,and are therefore capable of existing in two optically isomeric forms.The present invention includes the dextro- and laevo- rotatory isomersof each compound of the invention, and their mixtures in allproportions.

Particular examples of compounds according to the invention includethose listed in Table I below:

                                      TABLE I                                     __________________________________________________________________________     ##STR6##                                                                                                    PHYSICAL CONSTANT                              COMPOUND                       (MELTING POINT OR                              NO      Z   Y   R.sup.1                                                                            R.sup.9   BOILING POINT)                                 __________________________________________________________________________    1       CF.sub.3                                                                          H   CH.sub.3                                                                           OH        M.p. 100                                       2       CF.sub.3                                                                          H   CH.sub.3                                                                           OCH.sub.3 B.p. 134-138/0.05 Torr                         3       CF.sub.3                                                                          H   CH.sub.3                                                                           OC.sub.2 H.sub.5                                                                        oil                                            4       CF.sub.3                                                                          H   CH.sub.3                                                                           OC.sub.2 H.sub.7  -n                                                                    B.p. 155/0.05 Torr                             5       CF.sub.3                                                                          H   CH.sub.3                                                                           OC.sub.4 H.sub.9  -n                                                                    B.p. 167/0.05 Torr                             6       CF.sub.3                                                                          H   CH.sub.3                                                                           OC.sub.4 H.sub.9 sec                                                                    B.p. 167/0.05 Torr                             7       CF.sub.3                                                                          H   CH.sub.3                                                                           OC.sub.4 H.sub.9 iso                                                                    B.p. 165/0.05 Torr                             8       CF.sub.3                                                                          H   CH.sub.3                                                                           OC.sub.5 H.sub.11  -n                                                                   oil                                            9       CF.sub.3                                                                          H   CH.sub.3                                                                            ##STR7## oil                                            10      CF.sub.3                                                                          H   CH.sub.3                                                                            ##STR8## oil                                            11      CF.sub.3                                                                          H   CH.sub.3                                                                           OCH.sub.2 CH(C.sub.2 H.sub.5).sub.2                                                     oil                                            12      CF.sub.3                                                                          H   CH.sub.3                                                                           OC.sub.6 H.sub.13  -n                                                                   oil                                            13      CF.sub.3                                                                          H   CH.sub.3                                                                           Ocyclohexyl                                                                             oil                                            14      CF.sub.3                                                                          H   CH.sub.3                                                                            ##STR9## oil                                            15      CF.sub.3                                                                          H   CH.sub.3                                                                           OCH.sub.2 CH.sub.2 OCH.sub.3                                                            oil                                            16      CF.sub.3                                                                          H   CH.sub.3                                                                           OC.sub.8 H.sub.17  -n                                                                   oil                                            17      CF.sub.3                                                                          H   CH.sub.3                                                                           NHC.sub.2 H.sub.5                                                                       m.p. 96-98                                     18      CF.sub.3                                                                          H   CH.sub.3                                                                           NH.sub.2  m.p. 168-170                                   19      CF.sub.3                                                                          H   CH.sub.3                                                                           NHCH.sub.2 C.sub.6 H.sub.5                                                              m.p. 126-128                                   20      CF.sub.3                                                                          H   CH.sub.3                                                                           NH.C.sub.6 H.sub.4.Cl -p                                                                m.p. 147-149                                   21      CF.sub.3                                                                          H   CH.sub.3                                                                           NHCH.sub.2 CH.sub.2 OH                                                                  m.p. 72-74                                     22      CF.sub.3                                                                          H   CH.sub.3                                                                           NHNH.C.sub.6 H.sub.4.Cl -p                                                              solid                                          23      CF.sub.3                                                                          H   CH.sub.3                                                                           N(CH.sub.3).sub.2                                                                       oil                                            24      CF.sub.3                                                                          H   CH.sub.3                                                                           OCH.sub.2 CHCH.sub. 2                                                                   oil                                            25      CF.sub.3                                                                          H   CH.sub.3                                                                           OC.sub.6 H.sub.5                                                                        oil                                            26      CF.sub.3                                                                          H   CH.sub.3                                                                           OC.sub.6 H.sub.4.CH.sub.3  -m                                                           oil                                            27      CF.sub.3                                                                          H   CH.sub.3                                                                           OCH.sub.2 C.sub.6 H.sub.5                                                               oil                                            28      CF.sub.3                                                                          Cl  CH.sub.3                                                                           OH        m.p. 104-107                                   29      CF.sub.3                                                                          Cl  CH.sub.3                                                                           OCH.sub.3 oil                                            30      CF.sub.3                                                                          Cl  CH.sub.3                                                                           OC.sub.2 H.sub.5                                                                        oil                                            31      CF.sub.3                                                                          Cl  CH.sub.3                                                                           OC.sub.3 H.sub.7  -n                                                                    oil                                            32      CF.sub.3                                                                          Cl  CH.sub.3                                                                           OC.sub.3 H.sub.7 iso                                                                    oil                                            33      CF.sub.3                                                                          Cl  CH.sub.3                                                                           OC.sub.4 H.sub.9  -n                                                                    oil                                            34      CF.sub.3                                                                          Cl  CH.sub.3                                                                           OC.sub.4 H.sub.9 sec                                                                    oil                                            35      CF.sub.3                                                                          Cl  CH.sub.3                                                                           OC.sub.4 H.sub.9 iso                                                                    oil                                            36      CF.sub.3                                                                          Cl  CH.sub.3                                                                           OC.sub.5 H.sub.11  -n                                                                   oil                                            37      CF.sub.3                                                                          Cl  CH.sub.3                                                                            ##STR10##                                                                              oil                                            38      CF.sub.3                                                                          Cl  CH.sub.3                                                                           Ocyclohexyl                                                                             oil                                            39      CF.sub.3                                                                          Cl  CH.sub.3                                                                            ##STR11##                                                                              oil                                            40      CF.sub.3                                                                          Cl  CH.sub.3                                                                           OCH.sub. 2 CH.sub.2 OH                                                                  oil                                            41      CF.sub.3                                                                          Cl  CH.sub.3                                                                           OCH.sub.2 CH.sub.2 OCH.sub.3                                                            oil                                            42      CF.sub.3                                                                          Cl  CH.sub.3                                                                           OC.sub.8 H.sub.17  -n                                                                   oil                                            43      CF.sub.3                                                                          Cl  CH.sub.3                                                                           N(CH.sub.3).sub.2                                                                       oil                                            44      CF.sub.3                                                                          Cl  CH.sub.3                                                                            ##STR12##                                                                              m.p. 99-100                                    45      CF.sub.3                                                                          Cl  CH.sub.3                                                                           NHC.sub.6 H.sub.5                                                                       m.p. 135-136                                   46      CF.sub.3                                                                          Cl  CH.sub.3                                                                           NHNHC.sub.6 H.sub.5                                                                     m.p. 109-110                                   47      CF.sub.3                                                                          Cl  CH.sub.3                                                                           OCH.sub.2CH                                                                             m.p. 57.5-58.5                                 48      CF.sub.3                                                                          Cl  CH.sub.3                                                                           OCH.sub.2 CH.sub.2 Cl                                                                   m.p. 79.0-81.5                                 49      CF.sub.3                                                                          Cl  CH.sub.3                                                                           O.C.sub.6 H.sub.4.Cl -p                                                                 m.p. 63-64                                     50      CF.sub.3                                                                          Cl  CH.sub.3                                                                           SC.sub.6 H.sub.5                                                                        solid                                          51      CF.sub.3                                                                          Cl  CH.sub.3                                                                           NHCH.sub.3                                                                              m.p. 148-149                                   52      ClCF.sub.2                                                                        H   CH.sub.3                                                                           OC.sub.2 H.sub.5                                                                        oil                                            53      ClCF.sub.2                                                                        Cl  CH.sub.3                                                                           OC.sub.2 H.sub.5                                                                        m.p. 61-62                                     54      ClCF.sub.2                                                                        Cl  CH.sub.3                                                                           OCH.sub.2 CH.sub.2 Cl                                                                   oil                                            55      ClCF.sub.2                                                                        Cl  CH.sub.3                                                                           OCH.sub.2 CHCH.sub.2                                                                    oil                                            56      ClCF.sub.2                                                                        Cl  CH.sub.3                                                                           O.C.sub.6 H.sub.4.Cl -p                                                                 oil                                            57      ClCF.sub.2                                                                        Cl  CH.sub.3                                                                           NHCH.sub.3                                                                              solid                                          58      ClCF.sub.2                                                                        Cl  CH.sub.3                                                                           NHNH.C.sub.6 H.sub.4.Cl -p                                                              solid                                          59      CF.sub.3                                                                          Br  CH.sub.3                                                                           OC.sub.2 H.sub.5                                                                        oil                                            60      CF.sub.3                                                                          Br  CH.sub.3                                                                           OC.sub.4 H.sub.9  -n                                                                    oil                                            61      Cl  CF.sub.3                                                                          CH.sub.3                                                                           OC.sub.2 H.sub.5                                                                        oil                                            62      Cl  CF.sub.3                                                                          CH.sub.3                                                                           OC.sub.4 H.sub.9  -n                                                                    oil                                            63      Cl  CF.sub.3                                                                          CH.sub.3                                                                           OCH.sub.2 CH.sub.2 OCH.sub.3                                                            oil                                            64      Cl  CF.sub.3                                                                          CH.sub.3                                                                            ##STR13##                                                                              solid                                          65      Cl  CF.sub.3                                                                          CH.sub.3                                                                           NHC.sub.6 H.sub.5                                                                       solid                                          66      Cl  CF.sub.3                                                                          CH.sub.3                                                                           OCH.sub.2 C.sub.6 H.sub.5                                                               oil                                            67      Cl  CHF.sub.2                                                                         CH.sub.3                                                                           OC.sub.2 H.sub.5                                                                        oil                                            68      F.sub.2 CH                                                                        H   CH.sub.3                                                                           OC.sub.2 H.sub.5                                                                        oil                                            69      F.sub.2 CH                                                                        Cl  CH.sub.3                                                                           OC.sub.2 H.sub.5                                                                        oil                                            70      F.sub.2 CH                                                                        Br  CH.sub.3                                                                           OC.sub.2 H.sub.5                                                                        oil                                            71      CF.sub. 3                                                                         CF.sub.3                                                                          CH.sub.3                                                                           OC.sub.2 H.sub.5                                                                        oil                                            72      CF.sub.3                                                                          H   C.sub.3 H.sub.7  -n                                                                OC.sub.2 H.sub.5                                                                        oil                                            73      CF.sub.3                                                                          H   C.sub.2 H.sub.5                                                                    OC.sub.2 H.sub.5                                                                        oil                                            74      CF.sub.3                                                                          H   C.sub.3 H.sub.7 iso                                                                OC.sub.2 H.sub.5                                                                        oil                                            75      CF.sub.3                                                                          H   H    OC.sub.2 H.sub.5                                                                        oil                                            __________________________________________________________________________

The formulae of two further compounds not conveniently listed in Table Iare given below: ##STR14## In the case of a number of the compounds inthe above table, a physical constant in the form of a boiling point ormelting point is not available since the compounds were often isolatedby thin layer chromatography and a high proportion are viscous oils. Thestructure of the compounds was confirmed by examining their nuclearmagnetic resonance spectra, which corresponded with the structureassigned in Table I.

The compounds of the invention are herbicides which are in generalsubstantially more effective against grass species than againstbroad-leaved species of plants. They may be used to control unwantedgrass species growing alone, or at suitable rates of application theymay be used to control grass weeds growing among broad-leaved cropplants. The compounds may be either applied to the soil before theemergence of the unwanted grass species (pre-emergence application) orto the above-ground parts of growing grass plants (post-emergenceapplication).

In another aspect, therefore, the invention provides a process ofinhibiting the growth of unwanted plants, particularly grass species,which comprises applying to the plants, or to the locus thereof, aherbicidally effective amount of a compound of formula (I) ashereinbefore defined.

The amount of the compound to be applied will depend upon a number offactors, for example the particular plant species whose growth is to beinhibited, but in general an amount of from 0.025 to 5 kilograms perhectare is usually suitable, and preferably from 0.1 to 1.0 kilogramsper hectare. The skilled worker in the art will readily be able todetermine suitable amounts for use by means of standardized routinetests, without undue experimentation.

The compounds of the invention are preferably applied in the form ofcompositions, in which the active ingredient is mixed with a carriercomprising a solid or liquid diluent. Preferably the composition furthercomprises a surface-active agent.

The solid compositions of the invention may be for example, in the formof dusting powders, or may take the form of granules. Suitable soliddiluents include, for example, kaolin, bentonite, kiesselguhr, dolomite,calcium carbonate, talc, powdered magnesia, and Fuller's earth.

Solid compositions may also be in the form of disperisble powders orgrains comprising in addition to the active ingredient, a wetting agentto facilitate the dispersion of the powder or grains in liquids. Suchpowders or grains may include fillers, suspending agents and the like.

Liquid compositions include aqueous solutions, dispersions and emulsionscontaining the active ingredient preferably in the presence of one ormore surface active agents. Water or organic liquids may be used toprepare solutions, dispersions, or emulsions of the active ingredient.The liquid compositions of the invention may also contain one or morecorrosion inhibitors for example lauryl isoquinolinium bromide.

Surface active agents may be of the cationic, anionic or non-ionic type.Suitable agents of the cationic type include for example quaternaryammonium compounds, for example cetyltrimethyl ammonium bromide.Suitable agents of the anionic type include for example soaps, salts ofaliphatic mono-esters of sulphuric acid, for example sodium laurylsulphate; and salts of sulphonated aromatic compounds, for exampledodecylbenzenesulphonate, sodium, calcium and ammonium lignosulphonate,butylnaphthalene sulphonate, and a mixture of the sodium salts ofdiisopropyl- and triiso-propylnaphthalenesulphonic acid. Suitable agentsof the non-ionic type include, for example, the condensation products ofethylene oxide with fatty alcohols such as oleyl alcohol and cetylalcohol, or with alkyl phenols such as octyl-phenol, nonylphenol, andoctylcresol. Other non-ionic agents are the partial esters derived fromlong chain fatty acids and hexitol anhydrides, for example sorbitolmono-laurate; the condensation products of the said partial esters withethylene oxide and the lecithins.

The compositions which are to be used in the form of aqueous solutions,dispersions or emulsions are generally supplied in the form of aconcentrate containing a high proportion of the active ingredient, theconcentrate being diluted with water before use. These concentrates areusually required to withstand storage for prolonged periods and aftersuch storage to be capable of dilution with water in order to formaqueous preparations which remain homogeneous for a sufficient time toenable them to be applied by conventional spray equipment. In generalconcentrates may conveniently contain from 10 to 85% and preferable from25 to 60% by weight of active ingredient. Dilute preparations ready foruse may contain varying amounts of the active ingredient, depending uponthe purpose for which they are to be used; however, dilute preparationsuitable for many uses contain between 0.01% and 10% and preferablybetween 0.1% and 1% by weight of the active ingredient.

The compounds of the invention may be prepared from appropriatelysubstituted 2-halogenopyridines of formula (II): ##STR15## wherein Xrepresents a fluorine, chlorine, bromine, or iodine atom and Y and Z areas defined in formula (I) above. Three general routes are available forconverting the halogenopyridines (II) into compounds of the invention;these are described below as Routes A, B and C.

Route A is outlined in the following scheme:

Route A ##STR16##

In Route A, the symbols R¹, R², Z and Y have the meanings previouslyassigned to them, Hal stands for a halogen, preferably chlorine orbromine, and M is a cation, for example sodium.

In Route A, a suitably substituted halogenopyridine (II) is reacted witha metal salt of p-methoxyphenol, for example the sodium salt ofp-methoxyphenol. The reaction is preferably carried out in a solvent ordiluent, for example methyl ethyl ketone, tetrahydrofuran;dimethylsulphoxide or dimethylacetamide. The 2-p-methoxy-phenoxycompound (III) so obtained is then demethylated by a standard procedure,for example by heating with pyridine hydrochloride or with hydrogenbromide in acetic acid, to obtain the corresponding p-hydroxy compound(IV). This in turn is reacted in the form of its metal salt (for examplethe sodium or potassium salt) with the appropriate halogeno-alkanoicacid derivative (V) to obtain the required compound (I). Preferably thisreaction is carried out in a solvent or diluent, for example methylethyl ketone.

Route B is outlined in the following scheme: ##STR17##

According to Route B, an appropriately substituted 2-halogenopyridine(II) is reacted with hydroquinone in the presence of a base to give thep-hydroxyphenoxy compound (IV) already referred to in Route A. Thereaction is preferably carried out in a solvent or diluent for thereactants. Examples of suitable solvents include aprotic solvents, forexample dimethylformamide. The reaction is preferably accelerated byheating, for example to a temperature in the range from 50° to 150°. Thebase used in the reaction may be, for example, an inorganic base, forexample sodium or potassium carbonate.

The second stage of Route B is identical with the last stage of Route Aand requires no further description.

Route C ##STR18## According to Route C, an appropriately substituted2-halogenopyridine (II) is reacted with a 2-(p-hydroxyphenoxy)propionicacid derivative (VI) in the presence of a base, giving the compound ofthe invention (I) directly. The derivatives (VI) are known in themselvesor may be made by conventional methods. The reaction is preferablycarried out in the presence of a solvent or diluent for the reactants.Example of solvents include lower ketones, for example methyl ethylketone. The reaction may be accelerated by heating and may for examplebe conveniently carried out at the reflux temperature of the solvent.Examples of bases for use in the reaction include inorganic bases, forexample anhydrous potassium carbonate. The starting materials (II) usedin Routes A, B and C may themselves be prepared by various methods.Compounds containing a fluorinated alkyl group, for example, may beprepared by reacting a corresponding chlorinated compound with afluorinating agent so as to exchange some or all of the chlorine atomsfor fluorine atoms. Thus, 2-chloro-5-trifluoromethyl pyridine isobtainable by reacting 2-chloro-5-trichloromethylpyridine with afluorinating agent, for example antimony trifluoride or liquid hydrogenfluoride. By regulating the amount of fluorinating agent used in thereaction it is possible to obtain compounds with alkyl groups containingboth fluorine and chlorine atoms; for example,2-chloro-5-trichloromethylpyridine may be reacted with a limited amountof antimony trifluoride to obtain2-chloro-5-chlorodifluoromethylpyridine. In these halogen exchangereactions a proportion of the halogen substituent at the 2-position ofthe pyridine may also exchange, so that a proportion of the2-fluorinated compound may be obtained. This is of no practicaldisadvantage since the halogen at the 2-position is displaced in thesubsequent conversion of the halogenopyridine to the compound of theinvention. Certain of the chlorinated compounds required as startingmaterials are believed to be new compounds, for example2-chloro-5-trichloromethylpyridine and2,3-dichloro-5-trichloromethylpyridine. These compounds form a furtherfeature of the invention. In addition to their usefulness asintermediates for preparing the compounds of the invention, they havesome biological activity as insecticides.

The invention further provides a process of preparing2-chloro-5-trichloromethyl pyridine which comprises reacting3-methylpyridine with chlorine in the liquid phase under the influenceof ultraviolet light.

The reaction of 3-methylpyridine (as free base or in the form of a salt)with chlorine is generally carried out in an inert organic solvent.Conveniently the solvent is a halogenated hydrocarbon, e.g. carbontetrachloride; but other solvents may be used, e.g. hydrocarbons orethers, provided they do not react under the conditions employed to giveunacceptable quantities of undesired by-products. Reaction is slow at orbelow room temperature, and is therefore conveniently speeded up byheat; convenient reaction temperatures are for example in the range 50°to 130° C. The solution may be heated under reflux. It is preferred touse dry reactants and solvents. Ultraviolet light may be supplied to thereaction from a suitable electric lamp, which for greatest efficiencymay be immersed in the reaction mixture. The reaction generally givesrise to a mixture of products, from which the desired2-chloro-5-trichloromethylpyridine may be isolated by conventionalmethods, e.g. distillation.

In an alternative process for making 2-halogeno-3-or-5-trifluoromethylpyridines, a 2-halogeno-3- or -5-carboxypyridine maybe reacted with sulphur tetrafluoride in the presence of hydrogenfluoride, as shown below for 2-chloro-5-trifluoromethylpyridine:##STR19## Compounds containing a difluoromethyl group may be prepared bytreating the corresponding pyridine aldehyde with sulphur tetrafluoride,as shown below: ##STR20##

The invention is illustrated by the following Examples, in which allparts are by weight and all temperatures in degrees Centigrade unlessotherwise specified.

EXAMPLE 1

This Example illustrates the preparation of a compound according to theinvention, namely, ethyl alpha4(5-trifluoromethyl-2-pyridyloxy)phenoxypropionate (Compound No. 3).

(a) Preparation of 2-chloro-5-trichloromethylpyridine

2-Bromo-5-methylpyridine (55 g) in dry carbon tetrachloride (600 ml) wasfiltered and then treated with dry hydrogen chloride to give thehydrochloride salt. The solid which separated was broken up and themixture heated to reflux. Dry chlorine was passed through the boilingmixture for 61/4 hours with irradiation by an ultra-violet lamp placesinside the reaction flask. The mixture was then cooled, filtered andevaporated to a pale yellow liquid which solidified on cooling. This wasidentified as the required chloro compound by its nuclear magneticresonance spectrum.

(b) Preparation of 2-chloro-5-trichloromethylpyridine and2-chloro-5-difluorochloromethylpyridine

2-Chloro-5-trichloromethyl pyridine (18 g) and antimony trifluoride (50g) were heated together at 140°-145° C. for 1 hour. The mixture wascooled, mixed with ice and concentrated hydrochloric acid, and extractedwith ether. The extracts were washed with water, dried with magnesiumsulphate, and evaporated. The products from several such preparationswere combined and distilled at atmospheric pressure through a shortcolumn packed with Fenske rings. The product boiling at 124°-154° C. wascollected and identified as 2-chloro-5-trifluoromethylpyridine. Higherboiling fractions were redistilled at a pressure of 20 mm mercury togive 2-chloro-5-difluorochloromethylpyridine, boiling at 82° to 90° C.

(c) Preparation of 2-p-methoxyphenoxy-5-trifluoromethyl pyridine

Sodium hydride (4.2 g of 50% dispersion in oil, washed with petroleum)was stirred in dry dimethylsulphoxide (100 ml) and a solution ofp-methoxy phenol (10.4 g) in dimethylsulphoxide (100 ml) added over aperiod of a few minutes. The mixture was stirred for 30 minutes to formthe sodium salt. To the solution was added2-chloro-5-trifluoromethylpyridine (15.0 g) in dimethyl sulphoxide (80ml) over a period of a few minutes. The mixture was then heated to70°-75° for 3 hours and left to cool overnight. Thin-layerchromatography showed that only one compound was present. The mixturewas diluted to 1.5 liters with water, and then extracted with ether(3×600 ml). The ether extracts were washed several times with water andthen with molar sodium hydroxide solution, and finally with water (2×200ml). The ether extract was dried and evaporated to give the requiredpyridine compound as a brown oil.

(d) Preparation of 2-p-hydroxyphenoxy-5-trifluoromethyl pyridine

2-p-Methoxyphenoxy-5-trifluoromethylpyridine (10.5 g) in glacial aceticacid (100 ml) and 48% hydrobromic acid (50 ml) were stirred and heatedunder reflux for 71/2 hours. The solution was then evaporated and theremaining oil treated with sodium bicarbonate solution and shaken withether (2×300 ml). The ether extract was shaken with 2-molar sodiumhydroxide solution (200 ml) and then water (150 ml). The aqueous layerswere combined, acidified with 2-molar hydrochloric acid and extractedwith ether (2×300 ml). The ether extract was dried and evaporated togive a brown oil identified as2-p-hydroxyphenoxy-5-trifluoromethylpyridine.

(e) Preparation of Compound no. 3 of Table I

2-p-Hydroxyphenoxy-5-trifluoromethylpyridine (0.22 g), ethylalpha-bromopropionate (0.24 g) and potassium carbonate (0.18 g) inmethyl ethyl ketone (5 ml) were stirred, and heated under reflux for 2hours. The mixture was left to cool overnight, then filtered, and theresidue washed with methyl ethyl ketone. The filtrate and washings wereevaporated and the remaining oil subjected to a high vacuum to removetraces of solvent. The nuclear magnetic resonance spectrum of the oilwas consistent with the structure assigned and the compound wasidentified as compound no. 3.

(f) Preparation of compound no. 8

The product from (e) (0.3 g) was dissolved in n-pentanol (15 ml)containing concentrated sulphuric acid (2 drops). The mixture was heatedto reflux for 31/2 hours. The solvent was removed and the residue takenup in ether and washed with saturated sodium bicarbonate solution. Theether solution was dried and evaporated to a colourless oil which waspurified by preparative scale thin layer chromatography on silica gelwith an 80:20 mixture of petroleum (b.p. 60°-80° C.) and ether as thesolvent. The nuclear magnetic resonance spectrum of the productidentified it as the required pentyl ester.

(g) Preparation of Compound no. 1

The product from (e) (0.14 g) in isopropanol (2 ml) was stirred at roomtemperature for 13/4 hours with an aqueous solution of sodium hydroxide(1.6 ml of a solution containing 1 g NaOH per 100 ml water). The mixturewas evaporated in a vacuum and the residue taken up in water, acidified,and extracted with ether (2×50 ml). The ether extracts yielded an oilidentified as the required carboxylic acid.

(h) Preparation of Compounds 2, 4 to 7, and 14

Following the procedure described in paragraph (e) above, but using ineach case the appropriate alpha bromopropionic ester instead of ethylalpha bromopropionate, compounds no. 2, 4 to 7 inclusive, and no. 14were prepared.

(i) Preparation of 2[4(5-trifluoromethylpyridyl-2-oxy)phenoxy]propionylchloride

The carboxylic acid prepared as described in paragraph (g) above (1.2 g)was heated under reflux with thionyl chloride (20 ml) for 1 hour and theexcess of thionyl chloride then removed under reduced pressure. Theresidue was mixed with toluene and the toluene evaporated under reducedpressure to remove traces of thionyl chloride. The propionyl chloridederivative was obtained as an oil.

(j) Preparation of compound no. 17 to 23

The acid chloride as prepared in (i) above (0.78 g) was added to anexcess of aqueous ethylamine (20 ml; solution containing 70 g ethylamineper 100 ml). The excess of ethylamine solution was removed under reducedpressure. The residue was diluted with water and extracted with ether.The ether solution was washed with 2-molar hydrochloric acid and water,and dried and evaporated. The residue was recrystallized from petroleum(b.p. 60°-80°) to give the ethylamide (Compound no. 17) with a meltingpoint of 96°-98°.

Following this procedure, compounds 18 to 23 were prepared, using theappropriate amine instead of ethylamine in each case.

(k) Preparation of compounds 9 to 13, 15, 16, 24 and 27

The acid chloride as prepared in (i) above (0.87 g) was dissolved inallyl alcohol and heated at 100° for 1 hour. The excess of alcohol wasremoved under reduced pressure and the remaining oil washed with waterand 2-molar hydrochloric acid and dissolved in ether. The ether solutionwas dried and evaporated and the remaining oil purified by thin-layerchromatography on silica gel using a mixture of equal volumes of etherand petroleum (b.p. 60°-80°) as eluent. The allyl ester (compound no.24) was obtained as a colourless oil. Compounds 9 to 13, 15, 16 and 27were prepared by a similar procedure, using in each case the appropriatealcohol in place of allyl alcohol.

(1) Preparation of compounds 25 and 26

The acid chloride as prepared in (i) above (0.94 g) in dry ethercontaining pyridine (2 ml) was mixed with phenol (1 molar proportion)and the solution left overnight. The solution was evaporated and theresidue purified by thin layer chromatography to give compound 25 as aclear oil. Compound 26 was similarly prepared.

EXAMPLE 2

This illustrates the preparation of 2-chloro-5-trichloromethylpyridineby chlorination of 3-methyl pyridine under the influence of ultra-violetlight.

3-Methylpyridine (10 ml) was dissolved in dry carbon tetrachloride (300ml). The solution was heated to reflux (about 80°) and dry chlorine gaspassed through the boiling mixture for 3 hours while it was at the sametime irradiated internally from a 100 watt ultra-violet lamp producinglight of wavelength 185 nm. Preparation thin layer chromatography(silica, chloroform/cyclohexane) on an evaporated sample of the solutionthus obtained gave three main products in total overall yield of 10-15%;the most abundant of these was identified by its nuclear magneticresonance spectrum as the desired 2-chloro-5-trichloromethylpyridine.This was confirmed by mass spectrograph analysis of the solutionobtained. The other two major products were 2-chloro-3-trichloromethylpyridine and a di(trichloromethyl)pyridine, present in amount of abouthalf, and about one-tenth, respectively, of the major product.

EXAMPLE 3

This Example illustrates the preparation of2-chloro-5-trichloromethylpyridine from a salt of 3-methylpyridine.

3-Methylpyridine (15 g) in dry carbon tetrachloride (200 ml) was treatedwith dry HCl gas to give the hydrochloride. The oily mixture thusobtained was stirred and heated to reflux. Dry chlorine was was bubbledinto the refluxing mixture for 4 hours while illuminating it internallyfrom the ultraviolet lamp used in Example 1. The reaction mixture wasthen cooled, and separated by decantation into solution and oily solid.The latter was purified, and shown to contain unreacted 3-methylpyridinesalt. The former was evaporated to an oily semi-solid, which was shownby thin-layer chromatography to have the characteristics of2-chloro-5-trichloromethylpyridine.

EXAMPLE 4

This Example describes the preparation of2-chloro-5-trifluoromethylpyridine by a method alternative to that ofExample 1.

6-Chloronicotinic acid (23.6 g), sulphur tetrafluoride (37.4 g) andanhydrous hydrogen fluoride (18.7 g) were heated in an autoclave withstirring for 8 hours at 120°. The mixture was cooled, poured on to ice,and neutralised with concentrated sodium hydroxide to 0°. The mixturewas extracted with ether and the extracts washed with water, dried, andevaporated. The residue was distilled and the fraction boiling at140°-150° collected. Analysis indicated that this consisted of2-chloro-5-trifluoromethylpyridine with some2-fluoro-5-trifluoromethylpyridine.

EXAMPLE 5

This Example describes the preparation of2-chloro-5-trifluoromethylpyridine by a method alternative to that ofExamples 1 and 4.

2-Chloro-5-trichloromethylpyridine (30.8 g) and anhydrous hydrogenfluoride (80 g) were heated for 10 hours at 200° with stirring in anautoclave. The mixture was cooled, poured on to ice, and neutralized at0°. The mixture was filtered and the residue and filtrate extracted withether. The ether extracts were washed with water, dried, and evaporatedto give an oil. This was distilled and the fraction boiling at 140°-154°collected. Analysis indicated that this consisted of2-chloro-5-trifluoromethylpyridine with some2-fluoro-5-trifluoromethylpyridine.

EXAMPLE 6

This Example illustrates the preparation of compound no. 30 of Table Iby Route A.

(a) Preparation of 2-amino-3-bromo-5-methylpyridine

2-Amino-5-methylpyridine (108 g) in glacial acetic acid (300 ml) washeated to 90°-100° C. while bromine (160 g) in acetic acid (55 ml) wasslowly added with stirring. When addition was complete, the mixture wasstirred and heated for a further 30 minutes and then allowed to coolovernight. The solid which separated was filtered off and mixed with iceand the mixture neutralized with concentrated ammonia, keeping thetemperature at 0° to 5° C. The solid was collected, washed with water,and dried to give the bromo-compound.

(b) Preparation of 3-bromo-2-chloro-5-methylpyridine

The product from (a) (145 g) was dissolved in concentrated hydrochloricacid (750 ml) and water (450 ml) and the solution cooled to -10° C.Sodium nitride (54 g) in cold water (450 ml) was added dropwise withstirring over a period of 90 minutes while the mixture was kept at -5°C. The solution was stirred for a further 2 hours, and then basifiedwith concentrated ammonia, keeping the temperature below 20° C. Thesolid which separated was washed with water, dried, dissolved in ether(1500 ml) and washed with cold sodium hydroxide solution (1 M; 1 liter).The ether solution was washed twice with water (1 liter portions),dried, and evaporated to give the required3-bromo-2-chloro-5-methylpyridine.

(c) Preparation of 2,3-dichloro-5-trichloromethylpyridine

The product from (b) (64 g) in dry carbon tetrachloride (650 ml) wastreated with dry hydrogen chloride. The precipitate was broken up andthe suspension heated under reflux while dry chlorine was bubbled intothe mixture, with illumination from an ultra-violet light source. After41/2 hours, the mixture was cooled, filtered, and the filtrateevaporated to give the required 2,3-dichloro-5-trichloromethylpyridine.The mass spectrum was consistent with the structure assigned to thiscompound.

(d) Preparation of 2,3-dichloro-5-trifluoromethylpyridine

The product from (c) (1.0 g) and antimony trifluoride (3.0 g) wereheated together at 170°-180° for 30 minutes. The mixture was thencooled, mixed with ice and water, and extracted with ether. The etherextracts gave a brown oil containing a mixture of2,3-dichloro-5-trifluoromethylpyridine and3-chloro-2-fluoro-5-trifluoromethylpyridine with a minor amount of2,3-dichloro-3-chlorodifluoromethylpyridine.

(e) Preparation of 3-chloro-2-p-methoxyphenoxy-5-trifluoromethylpyridine

P-Methoxyphenol (1.5 g) was added to a suspension of sodium hydride (0.6g 50% oil dispersion, washed with petroleum) in dry dimethyl sulphoxide(30 ml) and the mixture stirred for 15 minutes. A solution of thecombined products (1.5 g) from several preparations carried out asdescribed in paragraph (d), in dimethylsulphoxide (20 ml) was added tothe reaction mixture and heated to 60° C. for four hours. A furtheramount of sodium hydride (0.3 g of 50% oil dispersion, washed withpetroleum), and potassium carbonate (1.38 g) was added. Heating wascontinued for another 4 hours. The mixture was poured into ice andwater, and extracted with ether (400 ml). The ether extracts were washedwith water, dilute sodium hydroxide, and water, dried, and evaporated togive the product.

(f) Preparation of 3-chloro-2-p-hydroxyphenoxy-5-trifluoromethylpyridine

The product from (e) (2 g) was heated with pyridine hydrochloride (20 g)at 170°-180° C. for 6 hours. The mixture was cooled, diluted with dilutehydrochloric acid, and extracted with ether. The ether extracts gave anoily solid which was purified by preparative thin layer chromatographyusing silica as the adsorbent and 6% ethanol-chloroform as the solvent.

(g) Preparation of compound no. 30 of Table I

The product from (f) (0.16 g), ethyl alpha bromopropionate (0.3 g), andpotassium carbonate (0.25 g) were heated and stirred under reflux inmethyl ethyl ketone (10 ml) for 2 hours. The mixture was cooled andfiltered. Evaporation of the filtrate gave an oil which was heated in avacuum to remove traces of solvent. The oil was identified as compoundno. 30 by examination of its mass spectrum and its purity was confirmedby gas-liquid chromatography.

2,3-Dichloro-5-trichloromethylpyridine was also prepared by analternative route, as follows: cl (h) Preparation of2-amino-3-chloro-5-methylpyridine

2-Amino-5-methylpyridine (10.8 g) in concentrated hydrochloric acid (100ml) was kept at 10°-15° C. while hydrogen peroxide (30%, 21 ml) wasadded dropwise with stirring. When addition was complete the mixture wasstirred for 11/4 hours without cooling, and poured on to ice (about 200g). The mixture was brought to pH 8-9 by adding concentrated ammoniadropwise, keeping the temperature at 0° C. by adding ice. The solutionwas extracted with chloroform (2×300 ml). The chloroform extractsyielded the required chloro-compound as a yellow solid.

(i) Preparation of 2-bromo-3-chloro-5-methylpyridine

The product from paragraph (h) (5.7 g) in hydrobromic acid (48%; 50 ml)was cooled to -15° C. to -10° C. and bromine (2.6 ml) was added dropwisewith stirring. The temperature was then kept at -5° C. to 0° C. whilesodium nitrite (5.53 g) in water (12 ml) was added dropwise over aperiod of 45 minutes. When addition was complete, the mixture wasstirred a further 30 minutes at 0° C. and poured on to ice. The mixturewas made slightly alkaline by dropwise addition of concentrated ammonia,keeping the temperature at 0° C. with added ice. The mixture wasextracted with ether (150 ml). The ether extract was washed with water,sodium bisulphite solution, and water, and then dried and evaporated.The residue was taken up in petroleum (b.p. 40°-60° C.) and the solutionfiltered and evaporated. The residue was identified as2-bromo-3-chloro-5-methylpyridine.

(j) Preparation of 2,3-dichloro-5-trichloromethylpyridine

The product from paragraph (i) (2.9 g) in dry carbon tetrachloride (25ml) was treated with dry hydrogen chloride to convert it to thehydrochloride. Chlorine was passed through the suspension which was keptat 80° C. and illuminated by an ultra-violet lamp inside the reactionflask. After three hours the solvent was removed, leaving a residue of2,3-dichloro-5-trichloromethylpyridine.

EXAMPLE 7

This Example illustrates the preparation of2,3-dichloro-5-trifluoromethylpyridine by fluorination of2,3-dichloro-5-trichloromethylpyridine, using a fluorinating agentalternative to that of Example 6.

2,3-Dichloro-5-trichloromethylpyridine (35 g) was heated with anhydroushydrogen fluoride (100 g) in an autoclave at 200° for 10 hours withstirring. The cooled reaction mixture was poured on to ice andneutralized with sodium hydroxide at 0°. The mixture was extracted withmethylene chloride (750 ml). The extracts were washed with water (500ml), sodium carbonate solution (500 ml) and water (500 ml(, dried, andevaporated. The remaining oil was distilled and the fraction of boilingpoint 77°-83°/25 Torr was collected and identified as the requiredpyridine derivative.

EXAMPLE 8

This Example further illustrates the preparation of2,3-dichloro-5-trifluoromethylpyridine.

Antimony trifluoride (61 g) was melted under a vacuum to removemoisture. The cooled material was broken up and heated to 65°-70° whileantimony pentachloride (6.6 g) was added dropwise with stirring.2,3-Dichloro-5-trichloromethylpyridine (40 g) was then added dropwise tothe mixture and the whole heated to 160° over 45 minutes. The mixturewas cooled and steam distilled. The oil which distilled over wasextracted with ether (2×100 ml). The ether extract was washed withtartaric acid solution then water, sodium bicarbonate, and water, anddried. The remaining oil was distilled. The fraction boiling at71°-80°/18 Torr was identified as the required pyridine derivative.

EXAMPLE 9

This Example illustrates the preparation of3-chloro-5-trifluoromethyl-2-p-hydroxyphenoxypyridine by Route B.

Dry dimethylformamide (30 ml) was de-aerated by heating under refluxunder a stream of argon for 30 minutes. Hydroquinone (4.95 g) andanhydrous potassium carbonate (6.84 g) were added and heated for 90minutes under reflux. 2,3-Dichloro-5-trifluoromethylpyridine (6.48 g) indry, de-aerated dimethyl formamide (30 ml) was added to the abovemixture over a period of 4 hours. The mixture was allowed to coolovernight and diluted with water (50 ml). The mixture was acidified withdilute hydrochloric acid and extracted with ether (2×400 ml). The etherextract was washed with water (2×500 ml) and extracted with dilutesodium hydroxide solution (300 ml). The ether extract was washed withwater and the aqueous fractions combined and re-acidified withhydrochloric acid. The acidified aqueous solution was extracted withchloroform (2×400 ml). The chloroform extract yielded a light brown oilwhich on trituration with petroleum (b.p. 30°-40°) gave a colourlesssolid identified as the required3-chloro-5-trifluoromethyl-2-p-hydroxyphenoxypyridine.

EXAMPLE 10

This Example illustrates the preparation of ethyl2[4(3-chloro-5-trifluoromethylpyridyl-2-oxy)phenoxy]propionate (compoundno. 30 of Table I).

The product from Example 9 (1.0 g) was stirred and heated under refluxin methyl ethyl ketone (25 ml) with potassium carbonate (0.5 g) andethyl 2-bromopropionate (1.0 g) for 4 hours. The mixture was cooled andfiltered and the filtrate evaporated to give an oil which was purifiedby thin-layer chromatography on two 2 millimeter thick plates, each 20by 20 centimeters in size, using a mixture of 20 volumes of ether and100 volumes of hexane as the eluent. The product was extracted withethanol. Evaporation of the ethanol gave a colourless oil identified ascompound no. 30 by its nuclear magnetic resonance spectrum.

EXAMPLE 11

Following the procedure described in Example 10, compounds no. 29, 31 to39, 41 and 42 of Table I were prepared, using the appropriate ester of2-bromopropionic acid in each case.

EXAMPLE 12

This Example illustrates the preparation of2[4(3-chloro-5-trifluoromethylpyridyl-2-oxy)phenoxy]propionic acid(compound no. 28 of Table I).

Compound no. 31 of Table I (2.19 g) in isopropanol (20 ml) was treatedat room temperature dropwise with a solution of sodium hydroxide (0.23g) in water (20 ml). The mixture was stirred at room temperature for 4hours, then diluted to 300 ml with water. The solution was extractedwith methylene dichloride (2×50 ml) and acidified with 2-molarhydrochloric acid. The acidified solution was extracted with methylenedichloride (2×150 ml) and the extract dried and evaporated to give anoil. This solidified on standing and was dried at 85° in a vacuum togive compound no. 28 with a melting point of 104°-107°.

EXAMPLE 13

This Example illustrates the preparation of compounds 43 to 45 and 48 to51 of Table I.

(a) Preparation of2[4(3-chloro-5-trifluoromethylpyridyl-2-oxy)phenoxy]propionyl chloride.

The carboxylic acid prepared by the method of Example 12 (16.5 g) wasdissolved in an excess of thionyl chloride (200 ml) and heated underreflux for 2 hours. The excess of thionyl chloride was removed underreduced pressure to give the acid chloride as a yellow oil. This wastaken up in dry ether (220 ml) and the solution used to preparecompounds 40, 43 to 45, 48 to 51 and 77 as follows. Since the proceduresare conventional, only brief details are given, and these are tabulatedbelow.

    __________________________________________________________________________    COMPOUND AMOUNT OF ACID                                                       NO       CHLORIDE SOLUTION USED                                                                          REACTANT AND PROCEDURE                                                                          PURIFICATION OF                  __________________________________________________________________________                                                 PRODUCT                          43       40 ml             20 ml of aqueous   *TLC                                                       dimethylamine at room                                                                           using silica gel/ether                                      temperature                                        44       20 ml             0.75 g of morpholine                                                                            Recrystallisation from                                      in ether (20 ml) at                                                                             petroleum (b.p.                                                               60-80°)                                              room temperature  and toluene                                                 overnight                                          45       20 ml             0.85 g aniline in Recrystallisation from                                      ether (20 ml) at room                                                                           petroleum (b.p.                                                               60-80°)                                              temperature overnight                                                                           and  -n-propanol                 48       20 ml             6 ml 2-chloroethanol                                                                            TLC                                                         2 hr at 100°                                49       20 ml             0.55 g  -p-chlorophenol,                                                                        TLC using silica gel/                                       1 ml pyridine, in 20                                                                            mixture of ether with                                       ml ether at room  petroleum (b.p.                                                               60-80°)                                              temperature overnight                                                                           in ratio of 1 volume to 5        50       20 ml             0.45 g thiophenol, 1                                                                            TLC as for compound 49                                      ml pyridine, 20 ml                                                            ether at room                                                                 temperature overnight                              51       1.5 g of acid     20 ml of 20% aqueous                                                                            Recrystallisation from                    converted to acid methylamine at room                                                                             petroleum (b.p.                                                               60-80°)                            chloride as above temperature       and toluene                      40       0.8 g of acid     20 ml of ethylene TLC using silica gel/            and      converted to acid glycol at room    ether                            77       chloride as above temperature for 3                                                             hours                                              __________________________________________________________________________     *TLC stands for thin layer chromatography                                

EXAMPLE 14

This Example illustrates the preparation of compound 46 of Table I.

The solution prepared in paragraph (a) of Example 13 (20 ml) was addedto a solution of phenyl hydrazine (0.95 g) in dry ether (20 ml) at roomtemperature and the mixture stirred overnight. The mixture was thendiluted with water and acidified with 2-molar hydrochloric acid. Theether layer was separated, washed with water, and dried. Evaporation ofthe ether gave the phenylhydrazide as a solid of melting point109°-110°.

EXAMPLE 15

This Example illustrates the preparation of compound no. 47 of Table I.

The solution prepared in paragraph (a) of Example 13 (20 ml) was addedto a solution of propargyl alcohol (0.25 g) in ether (20 ml) containingpotassium carbonate (0.75 g). The mixture was stirred at roomtemperature overnight. Chromatography indicated that no reaction hadtaken place. The mixture was filtered and the filtrate evaporated to anoil. Propargyl alcohol (5 ml) was added and the mixture heated for 2hours at 100°. The mixture was cooled and the excess of propargylalcohol removed under reduced pressure. The residue was purified by thinlayer chromatography, using silica gel as the solid phase and a mixtureof ether (1 volume) and petroleum (b.p. 60°-80°; 5 volumes) as theeluent. The product isolated in this way was a colourless oil whichsolidified on storage to give compound no 47 with a melting-point of57.5°-58.5°.

EXAMPLE 16

This Example illustrates the preparation of ethyl alpha4(5-difluorochloro-2-pyridyloxy)phenoxy propionate. (Compound no. 52) byRoute A.

(a) Preparation of 5-difluorochloromethyl-2-p-methoxyphenoxy pyridine

The 2-chloro-5-difluorochloromethylpyridine prepared in Example 1 (b)(1.0 g) in dimethylsulphoxide (10 ml) was added to a solution ofp-methoxyphenol (0.62 g) previously reacted with sodium hydride (0.24 gof 50% oil dispersion, washed with petroleum) in dimethyl sulphoxide (15ml). The mixture was stirred and heated to 60°-65° C. for 5 hours,poured into ice, and extracted with ether. The ether extracts werewashed with water, dilute sodium hydroxide, and water, dried, andevaporated to give an oil identified as the required p-methoxy compound.

(b) Preparation of 5-difluorochloromethyl-2-p-hydroxyphenoxypyridine

The product from (a) (1.0 g) was dissolved in glacial acetic acid (12ml) and aqueous hydrobromic acid (48%; 5 ml) added. The reaction mixturewas stirred and heated under reflux for 31/2 hours. The mixture wascooled and evaporated under reduced pressure. The residue was taken intoether and washed with sodium bicarbonate solution and water. The ethersolution was dried and evaporated to yield an oil which partiallysolidified. This was purified by preparative thin layer chromatographyon silica gel using a mixture of 6% ethanol in chloroform as thesolvent.

(c) Preparation of compound no. 52

The product from (b) (0.18 g) was heated under reflux for 21/2 hours inmethyl ethyl ketone (10 ml) with ethyl alpha bromopropionate (0.3 g) andpotassium carbonate (0.25 g). The mixture was cooled and the solidsfiltered off and washed with methyl ethyl ketone. The filtrate andwashings were evaporated in a vacuum to give an oil. The nuclearmagnetic resonance spectrum of this oil was consistent with itsstructure assignment as compound no. 52.

EXAMPLE 17

This Example illustrates the preparation of ethyl2[4(3-chloro-5-chlorodifluoromethylpyridyl-2-oxy)-phenoxy]propionate(compound no. 53 of Table I) using Route C

2,3-Dichloro-5-chlorodifluoromethylpyridine (1.0 g) and ethyl 2-(4-hydroxyphenoxy)propionate (1.0 g)

in methyl ethyl ketone (10 ml) containing potassium carbonate (1.0 g)were stirred and heated under reflux for 3 hours. The mixture was cooledand filtered. The residue was washed with methylethyl ketone and thefiltrate and washings evaporated under reduced pressure to give an oil.The oil was purified by thin-layer chromatography using silica gel asthe solid phase and a mixture of ether (1 volume) and petroleum (b.p.60°-80°, 4 volumes) as the eluent. The product was a colourless oilwhich solidified on storage to give compound no. 53 with a melting pointof 61°-62°.

EXAMPLE 18

This Example illustrates the preparation of compounds 54 to 58 of TableI.

(a) Preparation of propyl2[4(3-chloro-5-chlorodifluoromethylpyridyl-2-oxy)phenoxy]propionate

2,3-Dichloro-5-chlorodifluoropyridine was reacted with propyl2(4-hydroxyphenoxy)propionate in methyl ethyl ketone as described forthe corresponding ethyl ester in Example 17. The propyl ester soobtained was purified by dissolving it in a mixture of ether (1 vol.)and petroleum (b.p. 60°-80°, 4 volumes) and passing it through a columnof silica gel.

(b) Preparation of carboxylic acid from (a)

The propyl ester was dissolved in isopropanol and treated slowly withsodium hydroxide solution as described in Example 12. The carboxylicacid was isolated as described in Example 12.

(c) Preparation of acid chloride from (b)

The 2[4(3-chloro-5-chlorodifluoromethylpyridyl-2-oxy)phenoxy]propionicacid, prepared in (b) was heated at 100° C. for 2 hours with excess ofthionyl chloride and the excess of thionyl chloride then removed underreduced pressure. The acid chloride was then used to prepare compounds54 to 58 as follows. Since the procedures are conventional, only briefdetails are given, and these are tabulated below.

    ______________________________________                                        COMPOUND  REACTION PROCE- PURIFICATION OF                                     NO        DURE            PRODUCT                                             ______________________________________                                        54        Reflux with excess                                                                            TLC using silica gel/                                         of 2-chloroethanol                                                                            ether                                                         for 2 hours                                                         55        Reflux with excess                                                                            TLC using silica gel/                                         of allyl alcohol                                                                              ether                                                         for 2 hours                                                         56        Reaction with   Product substantially                                          -p-chlorophenol in                                                                           pure                                                          ether in presence                                                             of pyridine at                                                                room temperature                                                              overnight                                                           57        Reaction with   TLC using silica gel/                                         excess of aqueous                                                                             ether                                                         methylamine                                                                   solution                                                            58        Reaction with   TLC using silica gel/                                         excess of  -p-  ether                                                         chlorophenyl-                                                                 hydrazine                                                           ______________________________________                                    

EXAMPLE 19

This Example describes the preparation of3-bromo-2-chloro-5-trifluoromethylpyridine.

(a) Preparation of 3-bromo-2-chloro-5-pyridine carboxylic acid

3-Bromo-2-chloro-5-methylpyridine (30 g) in water (650 ml) containingpotassium permanganate (60 g) was stirred and heated under reflux for 3hours. Further potassium permanganate (20 g) was then added and themixture heated and stirred for another 21/2 hours. The mixture wassteam-distilled to remove unchanged starting material, and then filteredwhile hot. The residue was washed with hot water. The filtrate andwashings were cooled and acidified with concentrated hydrochloric acid.The solid which separated was extracted with ether. The ether extractwas dried and evaporated to give 3-bromo-2-chloropyridine-5-carboxylicacid.

(b) Preparation of 3-bromo-2-chloro-5-trifluoromethyl pyridine

The product from (a) (12 g), sulphur tetrafluoride (20 g) and anhydroushydrogen fluoride (10 g) were stirred and heated to 120° for 8 hours inan autoclave. The product was poured on to ice and neutralized withconcentrated sodium hydroxide at 0°. The mixture was extracted withether (3×100 ml) and the extracts washed with water, sodium bicarbonatesolution, and water. The extracts were dried and evaporated to give abrown oil. This was distilled and the fraction boiling at 88-93°collected. This was identified as3-bromo-2-fluoro-5-trifluoromethylpyridine.

The product of paragraph (b) was used as starting material for thepreparation of compounds 59 and 60 of Table I, following Route C.

EXAMPLE 20

This Example describes the preparation of2,5-dichloro-3-trifluoromethylpyridine and2,5-dichloro-3-difluoromethylpyridine.

(a) Preparation of 2,5-dichloro-3-trichloromethylpyridine and2,5-dichloro-3-dichloromethylpyridine

2,5-Dichloro-3- methylpyridine (37 g) in dry carbon tetrachloride (500ml) was treated with sufficient dry hydrogen chloride to precipitate thepyridine as its hydrochloride. The mixture was then stirred and heatedunder reflux while dry chlorine was passed through and the solutionirradiated by an internal ultra-violet lamp. Chlorination was continuedfor 31/2 hours and the solution then evaporated to give an oily solid.This was washed with petroleum (b.p. 30°-40°). The residue wasidentified as consisting mainly of 2,5-dichloro-3-trichloromethylpyridine. The filtrate was evaporated to give an oil identified asconsisting mainly of 2,5-dichloro-3-dichloromethylpyridine.

(b) Preparation of 2,5-dichloro-3-trifluoromethyl pyridine

2,5-Dichloro-3-trichloromethylpyridine from (a) above (30 g) inanhydrous hydrogen fluoride (90 g) was stirred and heated to 200° in anautoclave for 10 hours. The contents were cooled, poured into ice, andneutralized with concentrated sodium hydroxide at 0°. The aqueous layerwas decanted from the oily organic layer and the latter extracted withportions of methylene chloride (total 750 ml). The methylene chlorideextracts were dried and evaporated to give an oil. This was distilledand the fraction boiling at 70°-76° at 20 Torr collected. Analysisindicated that this comprised 2,5-dichloro-3-trifluoromethylpyridinecontaining about 10 percent by weight of5-chloro-2-fluoro-3-trifluoromethylpyridine.

(c) Preparation of 2,5-dichloro-3-difluoromethylpyridine

2,5-Dichloro-3-dichloromethylpyridine (20 g) in anhydrous hydrogenfluoride (60 g) was stirred and heated in an autoclave for 10 hours at200°. The mixture was then cooled, poured on to ice and neutralized withconcentrated sodium hydroxide solution at 0°. The aqueous layer wasdecanted from the organic layer and the organic layer dissolved inmethylene dichloride. The methylene dichloride solution was used toextract the aqueous layer. The methylene dichloride extract was washedwith water, sodium carbonate solution, and water, and then dried andevaporated. The remaining oil was distilled. The fraction boiling at 85°to 98° at 22 Torr was collected and redistilled in a micro spinning bandapparatus. The fraction boiling at 87°-87.5°/25 Torr was identified as95% pure 2,5-dichloro-3-difluoromethylpyridine.

The 2,5-dichloro-3-trifluoromethylpyridine obtained as described abovewas converted by Route C into compounds 61 and 62 of Table I, and the2,5-dichloro-3-difluoromethylpyridine was converted by Route C intocompound 67.

Compounds 63 to 66 were prepared by reaction of2[4(5-chloro-3-trifluoromethylpyridyl-2-oxy)phenoxy] propionyl chloridewith, respectively, 2-methoxyethanol, morpholine, aniline, and benzylalcohol, following the procedures described in paragraphs (j) and (k) ofExample 1. The propionyl chloride required for these preparations wasmade by reaction of the corresponding acid with thionyl chloridefollowing the procedure described in paragraph (i) of Example 1. Therequired carboxylic acid was obtained by hydrolysis of its propyl esterwith sodium hydroxide following the procedure described in paragraph (g)of Example 1.

EXAMPLE 21

This Example illustrates the preparation of ethyl2[(5-difluoromethylpyridyl-2-oxy)phenoxy]propionate (compound no. 68 ofTable I).

(a) Preparation of 2-chloro-5-formyl pyridine

2-Chloro-5-cyanopyridine (15 g) in 90% formic acid (60 ml) and water (15ml) was stirred at 55° and treated with Raney nickel/aluminum alloy (15g). The mixture was stirred at 55° for 91/2 hours and the warm solutionfiltered. The residue was washed with warm ethanol (ca. 25 ml) and thefiltrates combined and diluted to 600 ml with water. The solution wasextracted with ether (3×250 ml). The ether extract was washed withaqueous sodium carbonate and water, dried, and evaporated to give a paleyellow solid identified as 2-chloro-5-formylpyridine.

(b) Preparation of 2-chloro-5-difluoromethylpyridine

The product from (a) (9.9 g) and sulphur tetrafluoride (15.5 g) wereheated in an autoclave at 153°-155° for 6 hours. The autoclave was thencooled and vented. The mixture was basified with aqueous sodiumcarbonate and extracted with methylene dichloride. The methylenedichloride was dried and evaporated, and the remaining oil distilled.The fraction boiling at 156°-164° was collected and identified as2-chloro-5-difluoromethylpyridine containing some2-fluoro-5-difluoromethylpyridine.

(c) Preparation of compound no. 68

The product from (b) (0.44 g) and ethyl 2-(4-hydroxyphenoxy)propionate(0.63 g) in methyl ethyl ketone (10 ml) containing potassium carbonate(0.5 g) were stirred and heated under reflux for 131/2 hours. Themixture was cooled and filtered, and the filtrate evaporated. Theremaining oil was purified by thin layer chromatography using silica gelas the solid phase and a mixture of chloroform (75 parts by volume),petroleum (b.p. 60°-80°, 25 parts) and ethyl acetate (5 parts) as theliquid phase. The product obtained in this way was an oil.

EXAMPLE 22

This Example illustrates the preparation of ethyl2[4(3-bromo-5-difluoromethylpyridyl-2-oxy)phenoxy]propionate (compoundno. 70 of Table I).

(a) Preparation of 3-bromo-2-chloro-5-formylpyridine

3-Bromo-2-chloro-5-cyanopyridine (8.6 g) in 90% formic acid (40 ml) andwater (10 ml) were treated with Raney nickel/aluminum alloy (8.0 g) andthe mixture stirred and heated to 55°-60° for 6 hours. The mixture wasleft to stand for two days, and then filtered. The filtrate was dilutedto 500 ml with water and extracted with ether (2×250 ml). The etherextract was washed with aqueous sodium carbonate, dried, and evaporatedto give an oil. The oil was diluted with toluene which was then removedunder reduced pressure. The residue was diluted with a little ether, thesolution filtered, and the filtrate evaporated to give an oil identifiedas the required aldehyde.

(b) Preparation of 3-bromo-2-chloro-5-difluoromethylpyridine

The product from (a) (5.6 g) and sulphur tetrafluoride (9 g) were heatedin an autoclave for 6 hours at 150°. The autoclave was cooled and ventedand the contents treated with aqueous sodium carbonate. The solution wasextracted with methylene dichloride. The methylene dichloride extractwas dried and evaporated to give an oil which was distilled underreduced pressure. The fraction boiling at 85°-95°/15 Torr was collectedand identified as 3-bromo-2-chloro-5-difluoromethylpyridine containing asmall proportion of 2-chloro-3-fluoro-5-difluoromethylpyridine or its2-fluoro-3-chloro isomer.

(c) Preparation of compound no 70

The product from (b) (0.5 g), ethyl 2-(4-hydroxyphenoxy)propionate(0.465 g), and potassium carbonate (0.5 g) in methyl ethyl ketone (10ml) were stirred and heated under reflux for 51/2 hours. The mixture wasfiltered and evaporated to give a yellow oil. This was purified by thinlayer chromatography using silica gel as the solid phase and as theliquid phase the mixture described in paragraph (c) of Example. Themajor band was extracted with ethanol. Evaporation of the ethanolyielded an oil which gas-liquid chromatography showed to contain 96% ofthe main component. This was identified as compound 70 by its nuclearmagnetic resonance spectrum.

EXAMPLE 23

This Example illustrates the preparation of ethyl2[4(3-chloro-5-difluoromethylpyridyl-2-oxy)phenoxy]propionate (compoundno 69 of Table I) by Route C.

(a) Preparation of 2,3-dichloro-5-difluoromethyl

A mixture of 2,3-dichloro-5-formylpyridine (3 g) pyridine containing aminor proportion of 2,3,5-trichloropyridine, was heated with sulphurtetrafluoride (4.5 g) in an autoclave for 6 hours. The cooled reactionmixture was treated with aqueous sodium carbonate and extracted withmethylene dichloride. The extract was dried and evaporated and theresidue distilled in a micro spinning band apparatus. The fractionboiling at 65°-100° was collected. Gas-liquid chromatography indicatedthat this was a mixture of about 60% of 3-chloro-2-fluoropyridine and40% of the required 2,3-dichloro-5-difluoromethylpyridine.

(b) Preparation of compound 69

The product from (a) (0.65 g), and ethyl 2-(4-hydroxyphenoxy)propionate(1.0 g) were heated under reflux in methyl ethyl ketone (10 ml) withstirring for 41/2 hours. The solution was filtered, and the filtrateevaporated to give an oil. The oil was purified by thin-layerchromatography, using silica gel as the solid phase and a mixture ofchloroform (75 parts by volume), petroleum (b.p. 60°-80°, 25 parts) andethyl acetate (5 parts) as the eluent. The product eluted was a mixture.This was chromatographed again using a mixture of ether (1 part byvolume) and petroleum (b.p. 60°-80°; 2 parts) as the eluent. Two bandsdeveloped; the faster moving band was extracted with ethanol and theethanol extracts evaporated. The remaining oil was identified ascompound no. 69 by its nuclear magnetic resonance spectrum.

EXAMPLE 24

This Example describes the preparation of2-chloro-3,5-bistrifluoromethylpyridine.

(a) Preparation of 3,5-bis-trifluoromethylpyridine

3,5-Pyridine-dicarboxylic acid (17.5 g) containing a proportion ofpyridine 2,5-dicarboxylic acid was heated with sulphur tetrafluoride (72g) and hydrogen fluoride (40 g) in an autoclave for 8 hours at150°-151°. The cooled reaction mixture was neutralized at 0° withconcentrated potassium hydroxide solution. The mixture was extractedwith methylene dichloride, and the extract dried and evaporated. Theresidue was distilled and the fraction boiling at 119°-128° collected.The NMR spectrum indicated a mixture of 3,5- and2,5-bis-trifluoromethylpyridines.

(b) Preparation of 2-chloro-3,5-bis-trifluoromethyl pyridine

The foregoing product (3.0 g) in dry carbon tetrachloride (250 ml) wasstirred and heated under reflux while chlorine (dried) was passed slowlythrough the solution and the solution was irradiated by a UV lamp. After61/2 hours the carbon tetrachloride was distilled off and the residuedistilled in a spinning band apparatus. The fraction boiling at 75°-85°was collected and identified as2-chloro-3,5-bis-trifluoromethyl-pyridine containing a proportion of2,5- and 3,5-bis-trifluoromethylpyridine.

The 2-chloro-bis-trifluoromethylpyridine so obtained was converted intocompound 71 of Table I by following Route C.

EXAMPLE 25

This Example illustrates the preparation of compound no. 76.

2-(p-Hydroxyphenoxy)-5-trifluoromethylpyridine (1.0 g) was heated underreflux with 2-chloropropionitrile (1 molar equivalent) and potassiumcarbonate (1 g) for three days. The mixture was filtered and the solventremoved under reduced pressure to give an oil, which was purified bythin-layer chromatography on silica gel using a mixture of equal volumesof ether and petroleum (b.p. 60°-80°).

EXAMPLE 26

This Example illustrates the preparation of compound no. 73.

2-(p-Hydroxyphenoxy)-5-trifluoromethylpyridine (1.25 g), potassiumcarbonate (0.75 g), ethyl alpha bromobutyrate (0.96 g) and methyl ethylketone (25 ml) were heated under reflux for 6 hours. The cooled solutionwas filtered and the solution evaporated to give an oil. This waspurified by passage through a column of silica gel using a mixture of20% by volume of ether and hexane as the eluent. Compound no. 73 wasobtained as a colourless oil.

Following this procedure, but using the appropriate alpha bromo alkanoicester in place of ethyl alpha-bromobutyrate, compounds 72, 74 and 75were prepared. The starting esters were ethyl alpha bromovalerate, ethylalpha bromo isovalerate, and ethyl bromoacetate respectively.

EXAMPLE 27

This Example illustrates the herbicidal properties of the compounds ofthe invention. Each compound was formulated for test by mixing it with 5ml of an emulsion prepared by diluting 100 ml of a solution containing21.8 grams per liter of Span 80 and 78.2 grams per liter of Tween 20 inmethyl cyclohexanone to 500 ml with water. Span 80 is a Trade Mark for asurface-active agent comprising sorbitan monolaurate. Tween 20 is aTrade Mark for a surface-active agent comprising a condensate of twentymolar proportions of ethylene oxide with sorbitan mono-oleate. Themixture of the compound and the emulsion was shaken with glass beads anddiluted to 12 ml with water.

The spray composition so prepared was sprayed on to young pot plants(post-emergence test) of the species named in Table II below, at a rateequivalent to 1000 liters per hectare. Damage to plants was assessed 14days after spraying by comparison with untreated plants, on a scale of 0to 3 where 0 is no effect and 3 represents 75 to 100% kill. In a testfor pre-emergence herbicidal activity, seeds of the test species wereplaced on the surface of fiber trays of soil and were sprayed with thecompositions at the rate of 1000 liters per hectare. The seeds were thencovered with further soil. Three weeks after spraying, the seedlings inthe sprayed fiber trays were compared with the seedlings in unsprayedcontrol trays, the damage being assessed on the same scale of 0 to 3. Adash (--) in the table of results means that no test was made. Theresults are given in Table II below:

                  TABLE II                                                        ______________________________________                                                        PRE- (A)                                                                      OR                                                                            POST-                                                                         (B)                                                                           EMER-                                                         COM-  RATE OF   GENCE                                                         POUND APPLICATION                                                                             APPLI-   TEST PLANTS                                          NO.   kg/ha     CATION   Lt  To  Ot/Av Ll  Cn   St                            ______________________________________                                        1     0.4       A        0   0   2     3   0    3                                             B        0   0   0     0   0    0                             5     0.5       A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             8     0.4       A        --  0   3     3   0    3                                             B        --  0   3     3   0    3                             17    0.8       A        2   0   3     3   0    3                                             B        0   0   3     3   0    3                             18    0.8       A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             19    0.8       A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             20    0.8       A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             21    0.8       A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             22    0.8       A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             23    0.8       A        0   0   3     3   0    3                                             B        0   0   1     3   0    3                             24    0.08      A        0   0   3     3   0    3                                             B        0   0   1     3   0    3                             25    0.08      A        0   0   2     3   0    3                                             B        0   0   3     3   0    3                             26    0.08      A        0   0   1     3   0    3                                             B        0   0   3     3   0    3                             27    0.08      A        0   0   0     3   0    3                                             B        0   0   3     2   0    3                             29    0.08      A        0   0   3     3   0    3                                             B        0   0   3     3   0    --                            31    0.25      A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             41    0.08      A        0   0   3     3   0    3                                             B        2   0   3     3   1    --                            43    0.8       A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             44    0.8       A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             45    0.8       A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             46    0.8       A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             47    0.08      A        3   0   3     3   0    3                                             B        0   0   3     3   0    3                             48    0.08      A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             49    0.08      A        0   0   3     3   0    3                                             B        0   0   3     2   0    3                             50    0.08      A        0   0   3     3   0    3                                             B        0   0   3     0   0    3                             51    0.8       A        2   0   3     3   0    3                                             B        0   0   3     3   0    3                             52    0.4       A        --  0   1     0   0    2                                             B        --  0   3     2   0    3                             53    0.08      A        0   0   3     3   0    3                                             B        0   0   1     0   0    3                             59    0.08      A        1   0   2     3   --   3                                             B        0   0   2     3   0    --                            60    0.08      A        0   0   3     3   0    3                                             B        3   0   3     3   0    --                            61    0.08      A        0   0   0     3   0    2                                             B        0   0   3     2   0    --                            62    0.08      A        0   0   0     3   0    0                                             B        0   0   0     1   0    --                            73    10.0      A        3   0   3     3   0    3                                             B        1   0   3     3   0    3                             74    10.0      A        0   0   0     3   0    3                                             B        0   0   3     3   0    3                             75    10.0      A        2   0   3     3   0    3                                             B        3   3   3     3   0    3                             76    0.5       A        0   0   3     3   0    3                                             B        0   0   3     3   0    2                             77    0.08      A        0   0   3     3   0    3                                             B        0   0   0     0   0    --                            ______________________________________                                    

The names of the test plants are as follows:

    ______________________________________                                        Lt          Lettuce                                                           To          Tomato                                                            Ot/Av       Cultivated oats and wild oats (Avena fatua).                                  Wild oats are used in the post-emergence test                                 and cultivated oats in the pre-emergence                                      test.                                                             Ll          Lolium perenne (perennial rye grass)                              Cn          Cyperus rotundus                                                  St          Setaria viridis                                                   ______________________________________                                    

The results in Table II clearly illustrate the selectivity of thecompounds of the invention, the grass species used in the test beingseverely damaged or killed while the dicotyledonous plants wereessentially unharmed.

EXAMPLE 28

This Example illustrates the herbicidal properties of the compounds ofTable I. Tests were carried out as described in Example 27. The compoundwas formulated by mixing an appropriate amount of the compound with 5 mlof an emulsion prepared by diluting 160 ml of a solution containing 21.8grams per liter of Span 80 and 78.2 grams per liter of Tween 20 inmethylcyclohexanone to 500 ml with water. The mixture of the compoundand emulsion was shaken with glass beads and diluted to 40 ml withwater. Damage to plants was assessed on a scale of 0 to 5 where 0 is 0to 20% damage and 5 is complete kill. In the table of results, a dash(--) means that no test was made. The results are given in Table IIIbelow:

                                      TABLE III                                   __________________________________________________________________________                     PRE- (A) OR                                                          RATE OF  POST- (B)                                                    COMPOUND                                                                              APPLICATION                                                                            EMERGENCE                                                                              TEST PLANTS                                         NO      kg/ha    APPLICATION                                                                            Sb                                                                              Rp                                                                              Ct                                                                              Sy                                                                              Mz Ww Rc                                                                              Sn                                                                              Ip                                                                              Am Pi                                                                              Ca                                                                              Po                                                                              Xs                     __________________________________________________________________________     1      0.4      A        1 0 0 0 5  5  5 --                                                                              0 0  0 0 0 0                                       B        2 1 0 0 5  3  3 0 0 0  0 0 0 0                       5      0.5      A        0 0 1 0 5  5  5 1 1 1  0 0 0 3                                       B        0 0 0 0 5  4  3 0 0 0  0 0 0 0                       8      0.4      A        0 0 0 1 5  5  5 --                                                                              0 0  0 3 0 0                                       B        2 2 1 0 5  4  4 0 0 0  0 0 1 0                      30      0.4      A        0 0 1 0 5  5  5 --                                                                              0 2  1 0 1 0                                       B        1 0 1 0 5  5  5 1 0 0  0 0 0 0                      31      0.08     A        2 0 0 0 4  4  5 0 2 0  0 0 0 0                                       B        2 0 0 0 5  3  3 2 1 0  0 0 0 --                     52      1.0      A        0 0 0 0 4  5  5 --                                                                              0 1  0 0 1 0                                       B        0 1 2 0 5  4  4 1 0 0  0 0 2 0                      53      1.5      A        3 0 0 1 4  5  5 0 0 3  0 1 0 0                                       B        1 0 1 0 5  4  4 1 0 3  0 1 2 0                      59      0.5      A        2 1 0 0 4  4  5 2 0 1  0 0 0 --                                      B        0 1 0 0 5  3  3 0 0 0  0 0 0 0                      60      0.5      A        2 0 0 0 4  4  5 2 0 0  0 2 0 --                                      B        0 0 0 0 5  3  3 0 0 0  0 1 0 0                      61      1.0      A        0 0 0 0 4  2  2 2 0 0  0 0 1 --                                      B        1 1 1 0 5  3  2 0 0 0  0 0 1 1                      62      1.0      A        0 0 0 0 3  4  5 0 0 0  0 2 0 --                                      B        0 2 0 0 5  3  2 0 0 0  0 0 1 0                      67      1.0      A        1 0 0 0 4  5  5 2 2 0  0 0 --                                                                              0                                       B        0 0 0 0 5  4  3 1 0 1  0 0 0 --                     72      1.5      A        2 0 0 0 2  0  1 0 0 1  0 1 0 0                                       B        0 0 0 0 1  0  0 0 2 0  0 0 0 0                      __________________________________________________________________________                      PRE- (A) OR                                                          RATE OF  POST- (B)                                                   COMPOUND APPLICATION                                                                            EMERGENCE                                                                              TEST PLANTS                                        NO       kg/ha    APPLICATION                                                                            Ab Cv Ot/Av                                                                             Dg Pu St Ec Sh Ag Cn                     __________________________________________________________________________     1       0.4      A        0  -- 4   -- 4  4  5  5  5  0                                        B        0  0  4   3  0  3  5  5  3  0                       5       0.5      A        1  -- 4   5  0  4  5  3  3  1                                        B        0  0  4   3  0  4  5  5  3  0                       8       0.4      A        0  -- 4   -- 3  4  5  4  5  0                                        B        0  -- 4   4  1  4  5  5  4  0                      30       0.4      A        2  -- 5   -- 4  5  5  5  5  0                                        B        1  -- 5   5  3  5  5  5  5  0                      31       0.08     A        1  -- 4   5  4  4  4  3  0  0                                        B        0  0  3   -- 2  5  5  5  4  0                      52       1.0      A        0  -- 3   -- 1  4  5  4  5  0                                        B        0  -- 4   4  0  4  5  5  2  0                      53       1.5      A        0  -- 4   5  5  5  5  4  2  0                                        B        0  0  5   5  4  5  5  5  4  0                      59       0.5      A        0  -- 4   5  5  5  5  5  2  0                                        B        0  0  5   4  3  5  5  5  4  0                      60       0.5      A        0  -- 4   5  4  5  5  5  4  0                                        B        0  0  4   4  3  5  5  5  4  0                      61       1.0      A        0  -- 4   5  1  5  5  -- 4  0                                        B        1  0  3   4  2  4  5  5  3  0                      62       1.0      A        0  -- 4   5  2  5  5  4  2  0                                        B        0  0  4   4  2  5  5  4  2  0                      67       1.0      A        0  -- 5   5  4  5  5  4  1  2                                        B        0  0  3   -- 3  5  5  5  4  0                      72       1.5      A        1  -- 0   1  0  0  2  0  0  0                                        B        0  0  0   0  0  0  0  1  1  0                      __________________________________________________________________________

The names of the test plants were as follows:

    ______________________________________                                        Sb         Sugar beet                                                         Rp         Rape                                                               Ct         Cotton                                                             Sy         Soya bean                                                          Mz         Maize                                                              Ww         Winter wheat                                                       Rc         Rice                                                               Sn         Senecio vulgaris                                                   Ip         Ipomoea purpurea                                                   Am         Amaranthus retroflexus                                             Pi         Polygonum aviculare                                                Ca         Chenopodium album                                                  Po         Portulaca oleracea                                                 Xs         Xanthium spinosum                                                  Ab         Abutilon theophrastii                                              Cv         Convolvulus arvensis                                               Ot/Av      Cultivated oats and wild oats (Avena fatua)                                   Wild oats are used in the post-emergence test                                 and cultivated oats in the pre-emergence test                      Dg         Digitaria sanguinalis                                              Pu         Poa annua                                                          St         Setaria viridis                                                    Ec         Echinochloa crus-galli                                             Sh         Sorghum halepense                                                  Ag         Agropyron repens                                                   Cn         Cyperus rotundus                                                   ______________________________________                                    

EXAMPLE 29

This Example further illustrates the selective herbicidal activity ofthe compounds of the invention. Tests were carried out on a range ofcrop plants and weeds, in which the compounds were applied to the cropsat ten times the rate at which they were applied to the weeds. The testprocedure was similar to that described in Example 27. Damage wasassessed 20 days after spraying, on a scale of 0 to 10 where 0 is noeffect and 10 is complete kill. Each result given in the table below isthe mean figure for damage to three plants. The selective nature of theherbicidal compounds of the invention will be readily apparent from thetable of results, since even though the compounds were applied to thecrops at ten times the rate which caused severe damage to the grassspecies in the test, there was little or no damage to the crop plants.

    ______________________________________                                               RATE OF                                                                       APPLICATION                                                            COM-   (kg/ha)                                                                POUND  TO CROPS     CROPS     WEEDS                                           NO     AND WEEDS    Sy    Ct  Sb  Ec  Dg   Av   Al                            ______________________________________                                        2      0.25 + 0.025 0     0   0   3   2    2    3                             3      0.5 + 0.05   0     0   0   4   3    1    1                             4      0.75 + 0.075 3     --  0   9   9    6    6                             5      1.0 + 0.1    3     1   1   9   9    6    8                             6      0.25 + 0.025 0     0   0   6   5    2    0                             7      0.5 + 0.05   0     0   0   6   9    1    6                             8      0.75 + 0.075 1     2   0   9   9    5    9                             9      0.71 + 0.1   0     0   0   9   9    3    8                             10     0.25 + 0.025 0     0   0   1   0    0    0                             11     0.5 + 0.05   0     0   0   7   8    1    4                             12     0.75 + 0.075 0     2   1   9   9    6    9                             13     1.0 + 0.1    0     0   0   9   9    6    9                             14     0.25 + 0.025 0     0   0   5   7    2    3                             15     0.5 + 0.05   0     0   2   9   9    4    6                             16     1.0 + 0.1    0     0   0   9   9    5    9                             28     0.125 + 0.0125                                                                             0     0   0   2   1    1    1                             29     0.25 + 0.025 0     0   0   9   9    8    2                             30     0.5 + 0.05   0     1   0   9   9    9    8                             31     1.0 + 0.1    1     3   0   9   9    9    8                             32     0.125 + 0.0125                                                                             0     0   0   2   4    4    0                             33     0.25 + 0.025 0     0   0   9   9    8    4                             34     0.5 + 0.05   0     1   0   9   9    9    9                             35     0.75 + 0.075 0     2   1   9   9    9    8                             36     0.125 + 0.0125                                                                             0     1   0   6   8    5    2                             37     0.25 + 0.025 0     0   0   2   3    6    0                             38     0.5 + 0.05   0     1   0   9   9    9    8                             39     0.75 + 0.075 0     0   0   9   9    9    5                             40     0.125 + 0.0125                                                                             0     0   0   4   4    5    0                             41     0.25 + 0.025 0     0   0   9   9    8    5                             42     0.5 + 0.05   0     0   0   9   9    9    7                             ______________________________________                                    

The meanings of the abbreviations for the names of the test plants havebeen given in Example 28 except for Al, which stands for Alopecurusmyosuroides.

EXAMPLE 30

This Example illustrates the herbicidal activity of compounds of theinvention against a perennial grass species, in comparison with apreviously known herbicidal compound of a similar type. The previouslyknown compound was compound A below: ##STR21## Compound nos. 5 and 31 ofTable I were compared with compound A. In the test, pieces of therhizome of Sorghum halepense 5 to 8 centimeters long and containing 2 to3 nodes were buried in compost in plastic trays in the greenhouse. Thecompounds were formulated for test as described in Example 28. In apre-emergence test the compounds were sprayed on to the compost threedays after the rhizome segments had been buried. The surface was thencovered with more compost and watered. In a post-emergence test, therhizome segments were left for 20 days, when shoots with two to fourtrue leaves had emerged, and sprayed. Assessments of herbicidal damagewere made three weeks after treatment.

In the test, three replicates were used for each treatment. The resultsare expressed as percentage damage to the plants, and are the mean oftwo separate tests. The figures for percentage damage are given in thetables below:

    ______________________________________                                        PRE-EMERGENCE RESULTS                                                         COMPOUND      RATE OF APPLICATION, kg/ha                                      NO            0.125  0.25       0.5  1.0                                      ______________________________________                                        A             11     55          69  100                                       5            58     98         100   98                                      31            85     88         100  100                                      ______________________________________                                    

    ______________________________________                                        POST-EMERGENCE RESULTS                                                        COMPOUND      RATE OF APPLICATION, kg/ha                                      NO            0.125  0.25       0.5  1.0                                      ______________________________________                                        A             58     85          94  100                                       5            66     88         100  100                                      31            96     100        100  100                                      ______________________________________                                    

It can be seen from the above tables that the compounds of the inventionare more herbicidally effective than Compound A at lower rates.

EXAMPLE 31

This Example illustrates the herbicidal properties of further compoundsof the invention. The compounds were tested by the procedure set forthin Example 27 and the results expressed in the same way; the results aregiven in the following table, which may be regarded as a continuation ofTable II.

    ______________________________________                                                        PRE- (A)                                                                      OR                                                                            POST-                                                                         (B)                                                                 RATE OF   EMER-                                                         COM-  APPLI-    GENCE                                                         POUND CATION    APPLI-   TEST PLANTS                                          NO    kg/ha     CATION   Lt  To  Ot/Av Ll  Cn   St                            ______________________________________                                        54    1.0       A        0   0   3     3   0    3                                             B        2   1   3     3   0    3                             55    1.0       A        0   0   3     3   0    3                                             B        2   1   3     3   0    3                             56    1.0       A        0   0   3     3   0    3                                             B        1   0   3     3   0    3                             57    1.0       A        0   0   3     3   0    3                                             B        1   0   3     3   0    3                             58    1.0       A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             63    5.0       A        0   0   3     3   0    3                                             B        1   0   3     3   0    3                             64    1.0       A        0   0   0     3   0    3                                             B        0   0   0     0   0    3                             65    1.0       A        0   0   1     3   0    3                                             B        0   0   0     0   0    3                             66    1.0       A        0   0   3     3   0    3                                             B        0   0   2     3   0    3                             68    1.0       A        0   0   0     3   0    3                                             B        0   0   1     2   0    3                             69    1.0       A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             70    1.0       A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             71    1.0       A        0   0   3     3   0    3                                             B        0   0   3     3   0    3                             ______________________________________                                    

We claim:
 1. A compound of formula ##STR22## wherein each of Z and Y,which may be the same or different, is hydrogen, fluorine, chlorine,bromine, iodine or halomethyl which is trifluoromethyl, difluoromethylor chlorodifluoromethyl provided that at least one of Z and Y ishalomethyl, and R is methyl.